#tab ul {
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;
    justify-content: space-around;
}

#tab ul li {
    flex-basis: 20%;
    text-align: center;
    line-height: 40px;
    background-color: #ccc;
    border-radius: 6px;
}